The last radio I will introduce is R909-DSP. This receiver was designed and sketched by myself based on Jason's idea of the R909 receiver. I thought it worked for the time being, but there were some issues and items that were not achieved and I'm continuing to consider them.
Ever since I started this blog, I've been thinking about making an airband receiver using a DSP chip. This time it finally happened. The configuration is TA2003-Si5351a-Si4732-LM386.
When receiving Airband, the local oscillator from the Si5351a module is input to the TA2003 first-stage mixer section and converted to IF21.4MHz, and the Si4732 operates as an AM21.4MHz receiver. FM broadcasts are directly received by the Si4732 chip. For control, use ATmega328P with ARDUINO UNO loader installed. The operating style uses a rotary encoder and switches to select functions, set parameters, and memorize parameters by double-clicking the switch.
This receiver has two boards. The CPU, operation switches, and OLED are mounted on the PANEL board, and the front end, Si4732, LM386, and Si5351a modules are mounted on the RF board.
２PCBｓ
The PANEL board alone can also be used as a digital VFO for modifying analog station receivers, etc., and an additional Si5351a module can be mounted on the PANEL board. I also created a DEBUG-PANEL board to which WE1602A can be attached during debugging. This debug panel board was used to convert the Chinese Airband receiver kit (No. 1) into a digital VFO. The OLED display is at the limit of the ATmega328P's memory capacity, so the 1602A display is easier to use when tinkering with sketches.
Remodeled the Chinese airband receiver kit
Furthermore, the RF board has a pin header that allows you to add an ADX front-end filter board to the front-end section. I'm thinking of experimenting with an HF band DSP receiver in the future.
In addition, the width of the RF board has been made 83.5mm so that the RF board can be slid into the drawn aluminum case. In that case, combine it with an OLED version panel. The front and back panels of the case are made from circuit boards, making it neat and compact.
Next up is the R909 kit. This kit was developed by JasonKits. JasonKits is running as an e-commerce site by Ham on the island of Malta, which sells a variety of electronic circuit boards and kits. In the area of hams, he is distributing open source boards.
The TA2003 used is a chip that was used in 100 yen shop radios a while ago, and was a favorite among Japanese radio hobbyists. Toragi has published a book about designing radios using TA2003. Written by JA9TTT. AM/FM radio & transmitter production collection (CQ Bunko).
What makes the R909 unique is that it uses a TA2003 instead of a mixer such as the NE602 in the double super first mixer section, and the other TA2003 is configured as an AM/FM radio after the first IF.
There are some problems that have been dragging on since the R80 V7. Two relays are used to switch the AB and FM front end filter sections and to switch the parent radio's AM/FM. However, since the TA2003 switches the AM/FM input using an internal circuit, there is no need to externally switch the TA2003 input signal. Rather than that, the problem is that the external switch is left open when not in use. Especially in the AM position, the high gain FM side circuit input is open, causing oscillation. I found this out when MR.RADIO KITS IN JA pointed out this. Thank you for letting me know.
R909 has a double super radio with 1st IF: 10.7MHz-2nd IF: 455kHz, and a single super with IF: 10.7MHz for FM broadcasting receiver. The first IF is 10.7MHz, which is the case with all Chinese airband receiver kits, R80 and R909. This is caused by the availability of ceramic filters and discriminators for FM broadcasting, but images cannot be removed. In airband reception, if you set the upper heterodyne at 10.7Mhz-IF in the 118-136MHz band, the image will be at 118 + 10.7 * 2 = 139.4Mhz, which cannot be removed by the front-end filter. Therefore, I think it would be better to use an IF such as 21.4MHz for airband receivers.
Next up is the R80 kit. This kit seems to be developed and manufactured by the same manufacturer as the first model.
R80 front view
Mr.kon has reported of kit assembly on his blog. I asked Mr.kon some questions, bought a kit, and assembled it. Thank you for his cooperation. (⑲ Manufacture the Chinese AIR band receiver kit (R80 Aviation Band PLL Receiver Kit Aviation Radio Aircraft Tower Call DYI kit))
By the way, there are two versions of R80: V6 and V7. I bought the V6 and assembled it. These two have completely different circuit configurations. V6 has the configuration NE5204-NE602-TA7640-MC3361-FM62429-LM386.
The block diagram of R80
I think the sensitivity is good because it is a double super and has an LNA. However, Skelch is unstable, so it's noisy when used as a standby monitor. I tried modifying it.
On the other hand, V7 has the configuration TA2003-TA2003-FM62429-LM386.
![](http://ae01.alicdn.com/kf/S9e02df276b374effb8610a4299104d9dt.jpeg_240x240.jpeg")
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